In manufacturing products are typically assembled from multiple parts. Those parts are often made of different materials and/or constructed using different manufacturing steps. Consequently the yield of “good” assembled products is a function of at least two factors, control of the manufacturing steps to ensure functioning and/or in-specification components, and the specific tolerances of the assembled product.
In most cases, designers strive to ensure that individual components are manufactured with tight enough tolerances such that when the parts are brought together and assembled, the final product meets its overall specifications. For example, the process to cut glass for a window is usually sufficiently controlled so that it is neither too big nor too small for a corresponding window frame. Similarly, window frames are manufactured to a certain size and tolerance to ensure that the corresponding glass will fit. Accordingly, both the glass and the frame are cut to some nominal size(s) so that when assembled the gap between then is within the required gap specification. Despite variations between pieces during manufacturing, tolerances are sufficiently controlled to ensure that the pieces fit together appropriately.
However, when design tolerances approach or exceed the ability of the manufacturing processes to build individual components, the yield of assembled pieces decreases because the probability of finding two compatible components at random decreases. Situations like this can arise for cosmetic reasons, such as minimizing the gap between two pieces, or ensuring continuity of color between two different materials. For situations where the assembled design tolerances significantly exceed the manufacturing capability of components other techniques are required in order to maintain the yield of assembled products.
Therefore, accurate and reliable techniques for selecting parts for assembly of a manufactured product is desired.